Geology Ch. 4 & 5 Questions

it is similar because in both processes the temperature is decreasing and both substances are solidifying. They are different because magma can be made of many different types of rock and water is just two elements.

The Earth is heated by planetismal accretion, gravitational compression, differentiation into the crust, mantle, & core, and radioactive decay. The first igneous rocks formed from freezing magma

Decrease in pressure: a decrease in pressure permits melting because atoms are able to break free of solid mineral crystals. This occurs when hot mantle rock rises to shallower depths in the Earth. Addition of volatiles: when volatiles mix with mantle rock, they help break chemical bonds, volatiles also decrease a rock's melting temperature. Heat transfer from rising magma: surrounding crustal rock is melted.

Because it depends on the source, how it interacts with its surroundings (assimilation), and whether crystals sink as they form (partial melting and magma mixing).

Because it is less dense than surrounding rock and because the weight of the overlying rock creates pressure that squeezes magma upward.

Temperature: hotter magma is less viscous, volatile content: volatile atoms tend to break apart bonds and may accumulate to form bubbles, and silica content: mafic magmas are less viscous than felsic magmas.

The depth of the intrusion, the shape and size of a magma body: the greater the surface area for a given volume of intrusion, the faster it cools, and the presence of circulating ground water: water passing through magma absorbs and carries away heat

A dike is a tabular intrusion that cuts across pre-existing layer ( its vertical). A sill is a tabular intrusion that injects parallel layering (horizontal). A pluton is different because it is just a blob intrusion that ranges in size from tens of meters across tens of km across.

Extrusive rocks cool rapidly and have small grains. Intrusive rocks cool much slower and have more time to grow larger grains.

It cooled slowly at first and then was ejected from the volcano causing it to cool rapidly.

Magma upwells because of the stretching and plate tectonics. it cools at the surface creating igneous rock.

Hot mantle plumes. Magma from deep within the mantle melts through the crust which is what causes hot spot volcanoes to form.

-splitting a continent in 2 and creating a new Mid Ocean Ridge -Some of the magma erupts to form basalt; but some transfers heat to the continental crust, which then partially melts itself, producing felsic magmas that erupt to form rhyolite.

LIP's are huge volumes of igneous rock. . LIPs have a profound affect on the environment and any changes in ocean chemistry, global temperature, and atmospheric clarity triggered by an LIP eruption could even cause the extinction of a life form

As the asthenosphere rises it undergoes decompression which leads to melting.

Basaltic lava: low viscosity, very hot, flows quickly, creates pahoehoe and a'a, can flow long distances. Andesitic lava: flow is too viscous to flow far, tends to break up as it flows. Rhyolitic/Felsic lava: so viscous that it may pile up in a dome shaped mass, this can cause pressure to build up and eventually lead to explosive eruptions.

Pyroclastic flow is a fast moving avalanche that occurs when hot volcanic ash and debris mix with air and flow down the side of a volcano. Lahar is a thick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the flank of a volcano.

Shield volcanoes are broad domes, generally form from low viscosity basaltic lava flows. Effusive eruptions only. Cinder cones are cone-shaped piles of tephra, they are typically symmetrical and have deep craters at their summit. Pyroclastic eruptions only. Stratovolcanoes are also known as composite volcanoes, they are large, cone shaped and consist of alternating layer soft lava, tephra, and debris. Ex. Mt. Fuji. Alternate between effusive and pyroclastic eruptions.

Because of its viscosity. If it has high viscosity (felsic) then gas and volatiles cannot escape easily and pressure is built up causing an explosive eruption.

A plume is formed.

Huge sheets of low viscosity lava erupt and form huge sheets, these sheets can layer on top of one another forming plateaus.

island: basaltic lava continental: erupt both basaltic lava and rhyolitic pyroclastic debris hot-spot volcano: an isolated volcano not caused by movement at a plate boundary, but rather by the melting of a mantle plume

Threat of lava flows, pyroclastic flows, ash and lapilli, the blast, landslides, lahars, earthquakes, tsunamis, and gas (CO2).

recurrence intervals, earthquake activity, changes in heat flow, changes in shape, increases in gas and steam emission

Danger assessment maps, evacuation, and diverting flows.